A microelectrode system used in neuro-stimulation and neuro-sensing typically includes an array of microelectrodes used as signal sources or a sensor interface for generating or receiving electrical signals, thereby to stimulate or sense activities in tissues.
The microelectrodes in a neuro-stimulation or sensing device are typically connected to an electronic device, for example, a microchip, by interconnects. The electronic device is preferably be protected in a fluid impermeable package and the interconnects are the only part of the device that penetrate through the fluid impermeable package. In the development of a microelectrode array embedded in a substrate, the substrate/electrode structure preferably resists fluid penetration so as to ensure the electronic device is not damaged by short circuiting or corrosion. Fluid penetration through the electrode or substrate structure can occur in one of the following ways: 1) through the electrode itself, 2) through the substrate, or 3) along the interface between the electrode and substrate. Appropriate material selection for the electrode and the substrate and appropriate manufacturing process are needed to produce a fluid impermeable microelectrode system.
One conventional microelectrode system includes an array of microelectrodes patterned on a top side of a two-dimensional, rigid substrate (e.g. silicon wafer). This approach is capable of producing small microelectrodes; however, the total number and size of the microelectrodes are limited by the need to pattern electrical leads, which are on the same side of the substrate, for each electrode. As a result, wide channels need to be constructed on the substrate to accommodate the individual electrical lead for each electrode. Thus the number of the electrodes in a unit area is limited.
In some instances, such as retinal prosthesis applications, the target tissue is curved, and the microelectrode array should preferably conform to the target tissue structure to avoid damage to the tissue. The prior art microelectrode arrays generally fail to conform to a target tissue.
Therefore, there is need for an improved microelectrode system that overcomes one or more of the problems set forth above.